Most cigarette filters are composed of cellulose acetate fibers. Cellulose acetate fibers are prepared as follows. Specifically, cellulose acetate flakes are dissolved in a solvent such as acetone, thus obtaining a cellulose acetate spinning dope. The spinning dope is fed to a spinning nozzle device and is then spun using a drying spinning process in a high-temperature atmosphere, yielding cellulose acetate fibers.
In order to facilitate the manufacture of a cigarette filter, the cellulose acetate fibers for use in a cigarette filter have an overall fineness that is appropriately set and are provided in the form of a crimped tow. Then, the cigarette filter is manufactured in a manner in which the crimped tow made of cellulose acetate fibers is opened using a cigarette filter plug winding device, impregnated with a plasticizer, formed in a rod shape using a filter winding paper, and then cut to a predetermined length.
Cellulose acetate results from subjecting cellulose to acetic acid esterification, and is inherently biodegradable. However, cellulose acetate is not regarded as having sufficient biodegradability to solve environmental problems, which are recently on the rise.
For example, in the case where cigarette filters made of cellulose acetate fibers are buried in soil, the original shape thereof is still maintained for 1 to 2 years, and a considerably long period of time is required to completely biodegrade the cigarette filters buried in soil.
A cigarette filter is assembled into a cigarette product and thus distributed to consumers and provided for smoking, and is ultimately discarded after smoking. Also, cigarette filter material may be directly wasted as fabrication residue from cigarette filter manufacturing plants. Such cigarette filter waste is collected and treated by being buried. Furthermore, cigarette butts are not recovered as waste, but remain in the natural environment. Problems due to cigarette filter waste include not only visual quality problems but also the leaching of toxic chemicals, adsorbed by used cigarette filters, into the environment, thus entailing a potential biological risk.
To respond to such circumstances, a variety of methods have been devised for manufacturing biodegradable cigarette filters. Such methods include the addition of an additive for increasing the rate of degradation of cellulose acetate comprising a biodegradable polymer, the use of cellulose acetate having a low degree of substitution to increase biodegradability, and the use of a polymer composite having high biodegradability, such as PHB (poly-hydroxybutyrate)/PVB (polyvinyl butyral) and starch, as a filter tow material.
However, satisfactory commercial solutions for producing filters that are acceptable to consumers while degrading quickly enough to overcome waste problems have not yet been suggested. The reason is that methods for achieving a rate of biodegradation fast enough to solve environmental problems while still satisfying the tobacco flavor characteristics and absorption profiles of cigarette filters when smoked have not yet been realized.
In the case where a cigarette filter is manufactured using a crimped tow as a material therefor, when the crimped tow has high strength, cuttability deteriorates in the cutting process, and the cut section becomes poor, undesirably resulting in low filter preparation yield and a low production rate.
Accordingly, there is need to develop techniques for materials for cigarette filters having superior biodegradability and high processing efficiency in the manufacture of cigarette filters.